SIST EN 60835-2-11:2002

SLOVENSKI STANDARD
01-oktober-2002
Methods of measurement for equipment used in digital microwave radio
transmission systems - Part 2: Measurements on terrestrial radio-relay systems -
Section 11: Cross-polarization interference canceller (IEC 60835-2-11:1996)
Methods of measurement for equipment used in digital microwave radio transmission
systems -- Part 2: Measurements on terrestrial radio-relay systems -- Section 11: Cross-
polarization interference canceller
Meßverfahren für Geräte in digitalen Mikrowellen-Funkübertragungssystemen - Teil 2:
Messungen an terrestrischen Richtfunksystemen -- Hauptabschnitt 11:
Kreuzpolarisations-Interferenz-Unterdrücker
Méthodes de mesure applicables au matériel utilisé pour les systèmes de transmission
numérique en hyperfréquence -- Partie 2: Mesures applicables aux faisceaux hertziens
terrestres -- Section 11: Dispositifs d'annulation du brouillage de polarisation croisée
Ta slovenski standard je istoveten z: EN 60835-2-11:1997
ICS:
33.060.30 Radiorelejni in fiksni satelitski Radio relay and fixed satellite
komunikacijski sistemi communications systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

NORME CEI
INTERNATIONALE IEC
INTERNATIONAL 60835-2-11
Première édition
STAN DARD
First edition
1996-10
Méthodes de mesure applicables au matériel
utilisé pour les systèmes de transmission
numérique en hyperfréquence
Partie 2:
Mesures applicables aux faisceaux hertziens
terrestres
Section 11: Dispositifs d'annulation
du brouillage de polarisation croisée
Methods of measurement for equipment used in
digital microwave radio transmission systems
Part 2:
Measurements on terrestrial radio-relay systems
Section 11: Cross-polarization
interference canceller
© IEC 1996 Droits de reproduction réservés — Copyright - all rights reserved
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835-2-11 © IEC:1996 - 3 -
CONTENTS
Page
FOREWORD 5
INTRODUCTION 7
Clause
1 Scope 9
2 Normative reference 9
3 Static characteristics 9
3.1 C/N versus cross-polarization isolation (XPI) (flat fading condition)
3.2 XPI (or improvement factor) versus delay difference 13
3.3 XPI (or improvement factor) versus notch depth with dispersive signals 15
4 Dynamic characteristics 19
4.1 General considerations
4.2 Method of measurement
4.3 Presentation of results 19
4.4 Details to be specified 19
Figures
1 Example of cross-polar interference canceller operation
2 Example of the structure of cross-polar interference canceller 23
3 Set-up for C/N versus XPI measurement 25
4 Example for C/N versus XPI measurement result
5 Set-up for XPI or improvement factor versus delay difference measurement 29
6 Example of measurement results of XPI and of improvement factor versus
delay difference 31
7 Set-up for measurement of dispersive conditions 33
8 Example of measurement results of XPI and improvement factor 35
9 Illustration of sweep waveform for the measurement of dynamic characteristics 37
10 Example of measurement result of dynamic characteristics 39

835-2-11 © IEC:1996 -5 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
METHODS OF MEASUREMENT FOR EQUIPMENT
USED IN DIGITAL MICROWAVE
RADIO TRANSMISSION SYSTEMS -
Part 2: Measurements on terrestrial radio-relay systems -
Section 11: Cross-polarization interference canceller
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization
comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to
promote international cooperation on all questions concerning standardization in the electrical and
electronic fields. To this end and in addition to other activities, the IEC publishes International Standards.
Their preparation is entrusted to technical committees; any IEC National Committee interested in
the subject dealt with may participate in this preparatory work. International, governmental and
non-governmental organizations liaising with the IEC also participate in this preparation. The IEC
collaborates closely with the International Organization for Standardization (ISO) in accordance with
conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of the IEC on technical matters, express as nearly as possible an
international consensus of opinion on the relevant subjects since each technical committee has
representation from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the
form of standards, technical reports or guides and they are accepted by the National Committees in that
sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the
subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 835-2-11 has been prepared by subcommittee 12E: Radio-relay
and satellite communication systems, of IEC technical committee 12: Radiocommunications.
The text of this standard is based on the following documents:
Report on voting
FDIS
12E/263/FDIS 12E/271/RVD
Full information on the voting for the approval of this standard can be found in the report
on voting indicated in the above table.

835-2-11 © IEC:1996 – 7 –
INTRODUCTION
To make a more efficient use of the radio spectrum, multi-state modulation techniques are
employed. These techniques have improved the spectral efficiency of the radio channel by
increasing the number of modulation states for example 16 QAM, 64 QAM or 256 QAM.
Another attractive method for achieving the high spectral efficiency is to transmit two
different signals simultaneously on orthogonal polarizations at the same nominal carrier
frequency over the same hop. This method may double the transmission capacity of digital
radio systems but there is a limited isolation between the signals because the orthogonal
polarization cannot be perfectly achieved due to imperfect waveguide and antenna
alignments. Moreover, that limited isolation is still further reduced by various conditions
such as multipath propagation or rainfall, and is of a time-variant nature. Consequently,
dual-polarized channels sharing the same nominal carrier frequency face mutual inter-
ference. Therefore, in the case of high multi-state modulation, it is necessary to use
adaptive countermeasures against the cross-polarization interference. In practice, such
cross-polarization interference cancellers (XPICs) are usually included in demodulators.
Adaptive XPICs consist of i.f. or baseband transversal filters in order to handle dispersive
signals and interference due to multipath propagation. Moreover, there are two kinds of
transversal filters. One is the baud-space transversal filter and the other is the fractional-
space one, whose delay period per one tap is generally half of that of the baud-space
transversal filter.
An example of the XPIC operation is illustrated in figure 1. For convenience, the ortho-
gonal polarizations are referred as horizontal (H) polarization and vertical (V) polarization,
respectively. In the figure, the i.f. transversal filter is shown for simplicity. The operation of
the baseband transversal filter is essentially equivalent to that of the i.f. filter. The figure
illustrates how the XPICs operate by using the received V-polarization signal and
adjusting its amplitude and phase by means of the transversal filter.
As a result, the cross-polarization interference present in the received H-polarization
signal is reduced by subtracting the adjusted V-polarization signal (cancelling signal).
Modification of the amplitude and phase is accomplished over the entire bandwidth of
the signal, since the frequency characteristics of the cross-polarization interference are
different from those of the received cross-polarization main signal.
Figure 1 shows only the effect of V to H depolarization. There is also the effect of the H
to V depolarization. Therefore, practical XPICs have structures as shown in figure 2.
The transversal filters that cancel the cross-polarization interference depolarized from the
V-polarization signal are adaptively controlled to minimize the V component of the H error
signal.
The results of the measurements depend not only on the XPIC but also on the demodulator.
These measurements are only applicable if suitable i.f. interface points are available.

835-2-11 © IEC:1996 - 9 -
METHODS OF MEASUREMENT FOR EQUIPMENT
USED IN DIGITAL MICROWAVE
RADIO TRANSMISSION SYSTEMS -
Part 2: Measurements on terrestrial radio-relay systems -
Section 11: Cross-polarization interference canceller
1 Scope
This section of IEC 835-2 deals with measurement for cross-polarization interference
cancellers (XPIC) used in digital microwave radio-relay systems.
2 Normative reference
The following normative document contains provisions which, through reference in this
text, constitute provisions of this section of IEC 835-2. At the time of publication, the
edition indicated was valid. All normative documents are subject to revision, and parties to
agreements based on this section of IEC 835-2 are encouraged to investigate the possibi-
lity of applying the most recent edition of the normative document indicated below.
Members of IEC and ISO maintain registers of currently valid International Standards.
IEC 835-2-8: 1993, Methods of measurement for equipment used in digital microwave
radio transmission systems - Part 2: Measurements on terrestrial radio-relay systems -
Section 8: Adaptive equalizer
3 Static characteristics
3.1 C/N versus cross-polarization isolation (XPI)
(flat fading condition)
3.1.1 General considerations
Cross-polarization isolation (XPI) as defined for two radio waves transmitted with the same
power and o rt
hogonal polarizations, is the ratio at the reception point of the power
received from one of the waves to the power from the other wave, in the expected polarization
of the first wave.
At relatively high C/N values (low noise), the
BER is essentially determined by the XPI.
A constant BER, for example 10 -4 , resulting from the cross-polarization interference, will
depend on the XPIC performance. Furthermore, it is impo rtant to measure the lock-in
performance by decreasing the value of the cross-polarization interference from a lock-out
state as well as the XPIC performance (hereinafter referred to as ordinary performance
measurement) measured by increasing the value of the cross-polarization interference
from a lock-in state.
835-2-11 ©IEC:1996 – 11 –
At relatively low C/N values (high noise), the
BER is essentially determined by the noise,
and the cross-polarization interference will have little effect on the BER. At relatively high
XPI values (low cross-polarization interference), there is a point where two curves (with
and without the XPIC) meet (see figure 4). The point determines the operational limit of
the XPIC, beyond which the XPIC cannot reduce the interference.
At low XPI values (smaller than about 10 dB), the C/N values at the outputs of the XPIC
are sensitive to the phase relations existing within the simulated propagation model.
Therefore, if the XPIC is designed to operate for XPI values below 10 dB, a phase
variation should contribute a part of the measurement. It is recommended that the worst
case values of C/N be recorded in the results.
3.1.2 Method of measurement
The set-up for the measurements is shown in figure 3. The two modulators are driven by
different pseudo-random binary signals which do not correlate with each other. After the H-
and V-polarization signals are divided into main (cross-polarization main signal) and leaky
(cross-polarization interference) paths, the four path-lengths are adjusted at the inputs of
the receivers to have the same static path length. Adjustable noise (n) and adjustable
cross-polarization interference (i) are added to the two main signals.
When C/N and XPI are both higher than about 10 dB, the addition of noise and cross-
polarization interference to the cross-polarization main signal path may be omitted
because the effect on the measurement results is then negligible. This applies also to the
methods of measurement described in 3.2.2, 3.3.2 and 4.2.
C/N and XPI should be set for both (cross-polarization and co-polarizatio
...